Low profile mining vehicles such as scoops, haulers, equipment movers and the like, powered by electric batteries are well known in the art. With present technology, a fully charged battery is capable of powering such a vehicle for the duration of one working shift or slightly in excess of eight hours. It generally requires approximately eight hours to fully recharge one of these batteries. In addition, it is usually recommended to allow the newly charged battery to "cool" for a period of approximately eight hours to improve the batteries performance. Since it is desirable to use the mining vehicles for more than one shift in a 24 hour period, the batteries in the vehicle must be changed after every shift.
It is therefore expedient to be able to quickly and efficiently change a battery on the mining vehicle so that the vehicle may return to productive use rather than remaining idle. The batteries in these types of vehicles are bulky and heavy, some having a weight in the range of several thousand pounds. As a result, the batteries are not easily removed from or added to the vehicles without assistance from a powerized lifting mechanism.
Usually, the electric battery of an underground mining vehicle is arranged in a heavy steel-plate battery tray located at the rear section of the mining vehicle for acting as a counterweight to the useful load which is normally supported by the front section of the vehicle. The battery tray protects the battery against physical damage during the operation of the vehicle as well as during the changing of the battery. However, if the battery case itself is strong enough to protect the battery, then a separate battery tray may not be necessary or the battery case will be supported by a lifting mechanism located on the vehicle. Since different arrangements of the battery may be employed, for simplicity of the description, the term "battery" should be understood to designate the whole exchangeable battery set, including the battery tray, if the battery is arranged in such a tray.
During operation of the mining vehicles or similar vehicles, the battery is supported by the vehicle and connected thereto for providing the power necessary to operate the vehicle. It has been the common practice in the art to include a battery changing system on the vehicle to load and unload batteries from the vehicle. This task has generally been accomplished through the use of hydraulically powered lifting systems for vertically moving the battery during battery changing operations. The combination of the vertical motion of the battery provided by the battery changing system and the horizontal motion of the vehicle itself, enables the operator to unload the drained battery from the vehicle onto a stand or the floor of a battery changing station and to load a fresh or recharged battery from the battery changing station onto the vehicle.
There are generally two different types of battery changing systems which are well known in the art. In the first type, the battery lays on the bottom plate of the vehicle main frame, which bottom plate is uninterrupted or cut in a "u" shape. Two rigid vertical hydraulic cylinders, acting upon horizontal brackets on the left and right sides of the battery, move the battery up and down during a battery changing operation. The major disadvantage of this first type of battery changing system is that the battery cannot be moved in a position lower than its normal position on top of the vehicle bottom plate.
In the second type of battery changing system, the battery is loaded on and secured to a battery support, such as a fork or a platform or a "U" shaped structure. This battery support under the action of a vertical hydraulic cylinder, moves up and down during a battery changing operation. The battery support is guided to move in the vertical direction by two parallel members attached firmly to the main frame of the vehicle. This second type of battery changing system is similar to the well known load-lifting system of a fork lift truck. The major disadvantages of this second type battery changing system are: first, the vertical travel of the battery is very short because the lengths of the vertical hydraulic cylinders and parallel guides are limited by the height of the vehicle main frame, and second, the parallel guides of the battery support are complicated and unreliable because it is difficult to keep them clean in an underground environment.
A further problem associated with the previous apparatus for lifting the battery onto the vehicle is the tendency for the battery to be pushed along the floor or against a wall in order to get the lifting arms of the battery changer underneath the lifting edge of the battery. This significantly increases the possibility of damaging the battery and the support structure in the mine during a battery changing operation.
A further problem to be avoided is the instability of the lifting apparatus. Particularly, the movement of the vehicle with the battery, may generate a vibration within the apparatus, thereby creating stress in the apparatus and vehicle.